Coveter, early on with my wee I had the same problem, particularly with seat comfort and low back pain with my girlfriend, Cheryl. Our particular solution was to create a couple of items to give her a more comfortable and secure ride-- a passenger backrest, wraparound sheepskin seat cover and in her specific case, a sheepskin cover for the backrest pad. These items together have increased her comfort level on long rides.
We've produced and sold these items for a number of years now for the wee/Vee's and you can see them with information on my homepage below:
You mentioned ugly aluminum boxes -lol- and we have performed small alterations to the passenger backrest to work with some brands of hard luggage in the past. Any soft luggage works with the passenger backrest as is.
The backrest sells for $125, the passenger sheepskin seat cover sells for $50 and the backrest sheepskin cover sells for $30, shipping not included. I can offer you a package deal on these three items if you're interested, just contact me at CHERDAN@webtv.net
and we'll be happy to answer any specific questions you may have. Also, if any or all of the above items don't work out for you, you can simply return all or any part of the order for a full refund.
The passenger backrest is approximately 9 inches tall and this height seems to work for most gals but can be increased in height for you if needed.
If you choose to go with a hard topbox, the bolt-on backrest cushion we offer (also shown on my above homepage) along with the sheepskin cover for it is a very comfortable combination to attach to the topbox. Ride safe.